Agricultural Lime Requirement Calculator (Buffer pH, Texture, ECCE & Cost)

How it works

buffer method (to 6.5, 8″, 100% ECCE): tons ≈ 1.4 + (6.8 − buffer pH) × 5.1; × 0.62 for target 6.0, × 1.3 for 6.8–7.0 · texture method: tons = ΔpH × (sand 1.0 … clay 4.2) · product rate = tons ÷ (ECCE ÷ 100) × depth ÷ 8 · split when > 4 t/ac (2 t/ac surface)

How much lime a soil needs to reach a target pH depends less on the pH itself than on how strongly the soil resists change — its buffering capacity, which rises with clay and organic matter — so soil labs measure a buffer pH that directly indexes the lime requirement, or, lacking that, agronomists estimate it from texture. The lab's figure assumes pure, fine calcium carbonate mixed through the plough layer, and real lime is corrected for its effective neutralising value and the depth it is worked into, with surface applications on no-till and pasture reduced to smaller, more frequent doses because the lime only reaches the top few inches.

Worked example

A silt loam at pH 5.6 with a buffer pH of 6.4 needs about 3.4 tons of 100% ECCE lime per acre to reach 6.5; with 80% ECCE ag lime worked in 8 inches that is 4.3 tons — about 172 tons and $6,540 for 40 acres, best split into two applications. Without a buffer pH the texture table would estimate 0.9 pH units × 3.0 = 2.7 tons at 100% ECCE, showing why the buffer test is worth having.

Frequently asked questions